Swine flu vaccine manufactured by Sanofi Pasteur has been voluntarily recalled, not due to safety, but it’s not quite as potent as it should be, according to the Centers for Disease Control and Prevention.

Health officials say the vaccine, distributed for use in kids younger than 3 years old, should still protect kids from H1N1 flu.

Children who have already received the recalled vaccine don’t need to be re-vaccinated. However, children age 9 and under still need two doses of H1N1 vaccine at least 28 days apart.

About 5,100 doses of this vaccine have been shipped to Washington state. Health care providers should stop using this vaccine and wait for instructions on how to return it. The state Department of Health is working with local health agencies to track organizations that have received shipments and make them aware of the recall.

"I understand why parents might be concerned. Yet, it’s important for everyone to know that the vaccine is safe," says Washington state Secretary of Health, Mary Selecky. "Also, there are other options available for young children who still need to get the H1N1 vaccine."

This recalled product is a very small percentage of the more than 1.6 million doses of H1N1 vaccine that Washington has received, officials said.